The present invention relates to solar heaters and to a method of making solar heaters and especially to solar heaters which concentrate the solar energy hitting the surface of the solar collector and which track the sun during the daylight hours to increase the efficiency of the solar heater.
In the past, a wide variety of solar heaters and solar water heaters have been provided for heating or for providing heat for a variety of purposes. The most common type of prior solar heater probably involves solar panels which are flat panels usually having a serpentine tubing therethrough and a black coating and which may have a transparent cover thereover for heating water passing through the tubing. These solar panels are typically mounted on the top of a building facing south so that the sun will hit the panels during a good portion of the day. The liquid passing through the solar panels may then be collected in a hot water storage tank and used in heating a building or providing hot water for a building. Another common type of solar collector involves those having a parabolic or arcuate surface which, instead of being coated black, is a reflecting surface to reflect the energy hitting the surface against a tube placed on the focal line of a parabolic reflector. The tube can have a liquid passing therethrough and is heated by the sun being reflected directly against the tube. Because of the shape of parabolic collectors, they tend to lose efficiency if in a fixed position because of the sun shading portions of the collector as the earth rotates during the day, positioning the sun in different positions relative to the collector. The obvious solution to this type of solar heater is to provide for the slow rotation of the solar collector so that it follows or tracks the sun, thereby getting the greatest efficiency during daylight hours. This has been accomplished in a number of different ways, including having photocells positioned to recognize the positions of greatest energy to produce a signal in an electrical circuit which can rotate an electric motor for rotating the solar collector to follow the sun.
In my prior U.S. Pat. No. 4,194,492 for a Solar Heating Apparatus, an approximation of the movement of the sun during the day allowed a movement of a parabolic reflector by the gradual flow of a liquid between containers in different positions. It has also been suggested in a number of prior patents to provide solar collectors which attract the sun by positioning partially shaded cylinders or containers which produce a differential pressure in a gas, which can then operate a bellows or cylinder to continue to rotate a reflector directed at the sun responsive to the balancing of the pressure by an equal amount of sunlight hitting each pressurized and partially shaded container.
Typical examples of this prior art can be seen in U.S. Pat. No. 4,185,615 to Bottum for a solar collector structure which has partially shaded cylinders having pressurized gas driving a pair of bellows to rotate a solar collector structure. Similarly, in U.S. Pat. No. 4,275,712 to Baer a sun tracking device employs displaced heating surfaces for automatic morning reorientation. In U.S. Pat. No. 4,178,913 to Hutchinson, a solar collector system is driven by hydraulic cylinders; while the collector in U.S. Pat. No. 4,122,827 is motor driven. In U.S. Pat. No. 4,079,249 to Glenn a solar energy operated motor has a plurality of containers positioned in a variety of positions inside a larger container having a predetermined window allowing light to hit different containers at different times of the day to rotate a solar heater. Similarly, the Snyder U.S. Pat. No. 4,276,122 shows a solar distillation unit capable of working off of solar radiation.
The present solar collector operates on a principle similar to some of those taught in these prior patents by utilizing a pair of containers having a pressurized gas therein and being partially shaded so that the pressure differential is built up between the gases in the containers except when an equal amount of sunlight is hitting each container. The pressure differential then moves the solar collector to continuously align the solar collector with the sun. However, in contrast to the prior art use of bellows, and special shifting mechanism, the present invention uses a simple rotating mechanism adapted to rotate the solar collector on its frame using a pair of arcuate cylinders mounted to a frame and a pair of fixed pistons positioned therein and attached to the solar collector. The fluid from each container is directed into one of the cylinders to rotate the solar collector to track the sun during daylight hours. In addition, the method of making the solar collector in accordance with the present invention allows the solar collector to be made inexpensively for a highly efficient collector.